During the Phase I effort, a totally new type of passive microcontact printing tool was developed by Parallel Synthesis Technologies that can print microarrays of a quality, cost and speed previously unobtainable. Silicon micromachining techniques were employed to fabricate a robust, inexpensive and very high density "printing microtiter plate" which prints sub-nL individual samples from each well onto a microarray format. The technology is based on arrays (1536 or 6144 SBS format) of individually compliant, silicon-spring loaded, hollow bore nozzles, with print tips in the range of 25-1 OOum connected to reservoir wells of volume about 0-5 uL, which are filled by automated liquid dispensers. Very large numbers (up to 10,000 spots/tip/loading) of extremely uniform spots (%CV spot size for one pin approximately 2% and 100 pins is approximately 5%) can be rapidly printed at an estimated rate of 1-10 x 10^6 spots/hour/head with less than <0.07% missing spots. In Phase II, two print heads of full microscope slide size (25 x 75 mm) will be fabricated at 1536 to 6144 formats to give a total of 300 or 1200 tips/print head, respectively. A proposed printer design, where one of these arrays is selected from among many in a carousel, should allow microarray printing at an unprecedented rate. After fabrication and testing at Parallel, the print heads will be distributed to three collaborators to determine if this technology will produce DNA and protein microarrays of an improved quality in three different array fabrication settings. The parallel print head will be employed (a) to print a 44,000 spot viral DNA array in an academic research setting with Prof. J. DeRisi (UCSF), (b) to print several hundred spot prototype diagnostic arrays with Dr. T. Tisone (Biodot, Inc.) and (c) to print antibody arrays in microtiter plate formats with Dr. D. Bochkariov (BD - Clontech). If these printing tools provide the anticipated large improvements, then the testing, sale and distribution can employ the existing channels currently used by Parallel for its commercially successful Silicon Microarray(tm) technology based on individual silicon pins which has been very well received by the microarray community. A fundamentally new type of multilevel silicon etch process was discovered during the course of this work and a patent application is in preparation.